Effect of Physical Work and Sleep Loss on Recovery Sleep

The effect of exercise and sleep loss on sleep was studied in four groups of young, physically fit, well-trained U.S. Marine Corps male volunteer subjects. In the first study, Study 1, ten pairs of Marines were observed. One member of each pair was assigned to an exercise routine and walked on a treadmill in full combat gear at a speed that induced an elevated heart rate corresponding to 30% of the individual's VO2 max. Exercise periods lasted half an hour per hour for two 17-hr long periods of continuous work, designated CW1 and CW2. The two CW episodes were separated by a 3-hr nap. Individuals assigned the exercise routine spent the second half of each hour in the CW period performing cognitive tasks using a computer terminal. The remaining member of each pair was assigned to a non-exercise, 'control' routine. Study 1 consisted of two routines and data on the participants and were grouped as follows: (1) 'Nap/Exercise', and (2) 'Nap/No Exercise.' In a second study, Study 2, eight pairs of Marines participated. In Study 2 the experimental protocol was identical with Study 1 with the exception that neither the exercising subject nor the control subject were permitted to nap between CW1 and CW2.